Question

What is F-actin made up of and what is the function of G-actin in it?

1) F-actin is made up of two rows of G-actin and G-actin provides an active site for myosin binding.
2) F-actin is made up of two rows of G-actin and G-actin provides structural support to F-actin.
3) F-actin is made up of two rows of G-actin and G-actin helps in the contraction of muscle fibers.
4) F-actin is made up of two rows of G-actin and G-actin is responsible for the movement of organelles within the cell.

Answer 1

F-actin is composed of two intertwined strands of G-actin, which play a critical role in muscle contraction by providing binding sites for myosin. This interaction facilitates the sliding mechanism necessary for muscle fibers to contract. Actin also functions in cell division, aiding in cytokinesis.

Step-by-step explanation:

F-actin is made up of two intertwined strands of G-actin. These chains of G-actin monomers polymerize to create the helical structure of the actin filament, with each G-actin monomer providing an active site for myosin binding. The interaction between F-actin and myosin is crucial for the process of muscle contraction, with myosin heads attaching to these active sites on the actin filaments and, using ATP energy, 'pulling' the actin to slide past the myosin filaments. This sliding action is the basis for muscle fibers contracting. Additionally, actin has a role in processes such as cell division, where it works with myosin to form a cleavage furrow during cytokinesis.